This application claims the benefit of Japanese Patent Application Number 2000-219901, filed Jul. 19, 2000.
The invention relates to polishing compounds, i.e. polishing compositions, also called polishing slurries, which are used in the manufacturing processes of polishing the surfaces of semiconductor substrates of, for example, silicon wafers, semiconductors, multichip modules, and electronic parts other than silicon wafers and multichip modules and electronic parts. Further, the invention relates to, methods of manufacturing polishing compounds, and polishing methods using polishing compounds when polishing the surfaces of semiconductor substrates.
Chemical Mechanical Polishing, hereafter also called CMP polishing, uses known polishing slurries in which are dispersed silica particles in an aqueous medium. CMP polishing of a semiconductor substrate is divided into three steps, called stock removal polish, intermediate, polish and final polish. The condition of the substrate surface at the conclusion of the final polish is scratch-free and haze-free. Furthermore, a perfect mirror surface with flatness is obtained. Such a surface is further referred to as a planar polished surface on the semiconductor substrate.
In the manufacture of polishing slurries for semiconductor substrates, having high purity raw materials with minimized impurities, silica particles, for example, fumed silica particles synthesized in the gas phase, have been used. However, fumed silica particles aggregate to form secondary aggregated particles., it being necessary to break up the aggregated particles, and disperse or dissolve the aggregated particles in water. If the break-up of the aggregated particles is not sufficient, the polishing slurry becomes more viscous in storage and thereafter, when used in a polishing operation, produces defects, such as, the appearance of scratches on the surface of the polished semiconductor substrate.
Known methods to disperse the aggregated particles of fumed silica use known low-speed beads mill or high speed agitation type dispersion equipment, but are not sufficient to disperse the silica particles.
For a polishing compound which prevents the agglomeration of secondary particles of silica particles, in Japanese patent bulletin H11-279534 and Japanese patent bulletin H11-302633, adding water-soluble cellulose derivatives and water-soluble organic amines is disclosed. However, exposure of the polishing compound to sunlight or ultraviolet light causes deterioration by the photodecomposition reaction of water-soluble cellulose and chemical amines. Further, by adding 1xcx9c10 weight % of types of amines to polishing compounds, there is an increase in the biochemical oxidant demand (BOD) load in the waste water stream. In this connection, from the point of view of prevention of water pollution, the amount of BOD must be less than 10 ppm. Accordingly, before discharging waste water after polishing, using the activity of bacteria in activated sludge, treatment by reducing the concentration 1/1000xcx9c1/10000 is necessary, adding a cost burden.
What is needed is a polishing compound which does not easily deteriorate in purity and further when polishing does not leave behind scratches or haze (cloudiness) on the polished surface.
This invention, in order to resolve these problems, provides a polishing compound for a slurry excelling in long term storage stability in which there is little contamination by metal ions, and while storing the slurry for a long period of time, neither agglomeration and settling nor, by the previous addition of chemicals to the slurry, discoloration by photodecomposition occurs.
The invention is to offer a polishing compound which also has excellent properties such that the combined abrasives contained in the slurry do not easily scar the substrate or said polishing layer with scratches or haze (cloudiness).
Further, the invention provides a method of polishing semiconductor substrate surfaces using a polishing compound.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, according to which:
FIG. 1 is a photomicrograph of crystal silica particles
FIG. 2 is a photomicrograph of cocoon-shaped colloidal silica particles
FIG. 3 is a graph showing evaluation results of various slurries
FIG. 4 is a graph showing evaluation results of various slurries
FIG. 5 is a graph showing slurry defects according to number of LPDs. And
FIG. 6 is a graph showing slurry haze